1. Field of the Invention
The present invention relates to a high intensity discharge (HID) lamp and in particular to an improved lamp holder for the HID lamp.
2. The Prior Arts
Currently, halogen lamps are generally used as car headlamps. It cannot provide with higher brightness due to limitation of tungsten filament material. A conventional 60 W halogen headlamp may generate a color temperature of about 3,000-3,200 K; if it is replaced with 100 W, the color temperature is at most increased to about 3,400-3,800 K. Hence, tungsten filament lamps have limitation for being employed as higher brightness car headlamps. Thus, other types of lamps, which can be substitutes for halogen lamps and provide higher brightness with low power consumption, are developing.
An existing HID lamp employed in vehicles is illustrated as an example of luminescence theory. Gases between two electrodes are excited by electrons and then ionized so as to excite phosphor to emit light. The HID lamps may be classified into low HID lamps, such as fluorescent lamps, and high HID lamps, such as high intensity mercury lamps, high intensity sodium vapor lamps and metal halide lamps. The HID lamp for vehicles is one of the high intensity discharge lamps. Xenon is injected into a crystal ball inside a quartz tube, and a stabilizer is employed to lift a voltage of a vehicle battery from 12 V to 23,000 V so that Xenon is excited by electrons and then ionized to generate electric arc and emit light.
HID lamps are brighter by three times than conventional halogen lamps, longer service life by five times than the conventional halogen lamps, and half power consumption as much as the conventional halogen lamps. As a result, it gradually becomes popular in the market of vehicle lamps.
As shown in FIG. 1, a conventional HID lamp mainly comprises a sleeve 1, a lamp tube 2, a lead wire 8, a metallic positioning member 6 having a vibration-damping clamping ring 5, and a base 3. The positioning member 6 has a ditch 4 on a bottom ring thereof for receiving the sleeve 1, and three iron sheets extending inwards and upwards from a top rim of the bottom ring, which are distributed in uniform and coupled with the clamping ring 5. The base 3 has a recess and a circular ring 7 received in a center of the recess. The positioning member 6 is received in the recess of the base 3, and the lamp tube 2 goes through the clamping ring 5 and then is mounted to the circular ring 7 of the base 3; in the meantime the sleeve 1 is mounted to the ditch 4 of the positioning member 6.
FIG. 2 illustrates a perspective view of the conventional HID lamp after assembled.
In the conventional lamp holder design, the bottom ring of the metallic positioning member 6 has to be manufactured to match with the recess of the base 3, which has a larger inner diameter, thereby having higher manufacturing cost. Next, the three iron sheets are used to support the clamping ring 5 to fix the lamp tube 2, which has not only higher manufacturing cost, but also more complicated structure. Thus, it is desired to provide an improved lamp holder for a HID lamp, which has structure and lower manufacturing cost.